About

Jeffrey Williams is a professor whose research focuses on commodity markets, financial markets, finance, public finance, mathematical programming, econometrics, and economic history. His work involves applying these areas to agricultural and resource economics, contributing to the understanding of market dynamics, policy analysis, and economic history within the agricultural sector. As a faculty member at UC Davis, he is engaged in teaching and research that support the development of economic policies and strategies related to agriculture and resource management.

Research topics

• Business
• Economics
• Engineering
• Environmental economics
• Ecology
• Agricultural economics
• Waste management
• Market economy
• Financial system
• Transport engineering
• Finance
• Biology

Selected publications

• Medicaid Nutrition Supports Associated With Reductions In Hospitalizations And ED Visits In Massachusetts, 2020–23

  Health Affairs · 2025-04-01 · 11 citations

  articleOpen access

  The Massachusetts Medicaid and Children's Health Insurance Program launched the Flexible Services Program to address food insecurity through partnerships with social service organizations under its Section 1115 demonstration waiver. We evaluated the effects of Flexible Services Program nutritional services (or Food Is Medicine programs) on health care use and costs during the first three-year program cycle (January 2020-March 2023). Our analyses pooled data on 20,403 Flexible Services Program participants from seventeen accountable care organizations. In propensity score-weighted analyses, program participation was associated with a 23 percent reduction in hospitalizations and a 13 percent reduction in emergency department visits compared with the number of hospitalizations and visits for 2,108 eligible nonparticipants. Modestly lower health care costs for Flexible Services Program participants were not statistically significant. Health care costs were $1,721 lower among participants after the COVID-19 emergency (2022-23) and $2,502 lower among adults with more than ninety days of enrollment during all study years (2020-23). These findings are important for Medicaid policy nationwide as other state Medicaid programs pursue similar Section 1115 demonstrations.

  PublisherDOI

• Conservation implications of wide-ranging year-round movement and distribution of Aleutian Island breeding <i>Aethia cristatella</i> (Crested Auklets)

  Ornithological applications · 2025-03-10 · 1 citations

  articleOpen access

  ABSTRACT Despite representing a crucial conservation concern, challenges in measuring seabird movement outside the breeding season remain. Among Alcidae, at least preliminary year-round movement data from representative populations has been obtained from only about half of extant species. During 2011–2015, we quantified year-round movement of Aethia cristatella (Crested Auklets) from breeding sites at Buldir and Gareloi islands, western Aleutian Islands, Alaska. We hypothesized that (1) individuals originating from these colonies use the Unimak Pass area in winter, and (2) periods of migration are associated with more time flying and less time resting on the sea. We captured adults (mean mass = 260 g) that were brooding nestlings and fitted them with 2-g (n = 31) and 1-g (n = 185) leg-attached archival light-based geolocation tags. Upon recapture, we obtained tracks from 3 of 31 individuals traveling with the 2-g tag and 93 of 185 individuals with the 1-g tag. Tagged individuals moved north immediately after chick-fledging, concentrated in the Chukchi and northwestern Bering seas through November, moved southwest to concentrate near the Kurile Islands (95%), or eastern Bering Sea shelf and eastern Aleutian passes (5%), including the vicinity of Unimak Pass, for January–March, and were back near breeding colonies by mid-April. No significant differences were detected in movement phenology between colonies, sexes, or years. Tag wet–dry data did not show a disproportionate time dry on days of continuous flying, suggesting movement fits the “fly and forage” migration model. Long-distance triangular migration between two distinct areas of concentrated use (Chukchi Sea and Kurile Islands), apparently to exploit seasonal prey availability, indicates where this species may be vulnerable to anthropogenic stressors such as oil and gas development and commercial fishing. Yet, the full pattern of variation of A. cristatella movement over time remains uncertain, requiring additional measurements in the field.

  PublisherOA PDFDOI

• Limited evidence that asymmetries of multiple Whiskered Auklet (<i>Aethia pygmaea</i>) feather ornaments could serve a display function

  Ibis · 2023-04-01

  article

  Elaborate avian feather ornaments have proven to be enigmatic because their function is often unclear, even though they are used in courtship and social displays. Male and female Whiskered Auklets Aethia pygmaea display on their faces four elaborate feather ornaments that serve both courtship and mechanosensory functions: three bilateral pairs of white facial plume tracts (superorbital, suborbital and auricular) and a slender black forehead crest, each consisting of several filoplumes. We studied left–right symmetry in the three antenna‐like bilateral white head plumes of 721 wild‐caught marked individuals (162 of known sex, 94 of known age that were 1–16 years old) during 1992–2009. Auricular and suborbital plumes were slightly more asymmetric in subadults (1‐year‐olds) than in adults (≥ 2 years old) but the opposite was true for superorbital plumes. Ornament asymmetries were not sexually dimorphic, nor were they significantly related to individual body condition, body size or age, except that superorbital plume asymmetry decreased significantly with tarsus length. Relative asymmetry (scaled for ornament size) of all three ornaments was negatively correlated with plume size, as predicted by some sexual selection models, but variation in asymmetries was large and differences between left (L) and right (R) sides in most birds were probably too small to be detected visually. Marginal mean absolute asymmetries (|L–R|) of super‐ and suborbital plumes were correlated with ocean climate during the preceding year when the birds would have been moulting, suggesting that fluctuating asymmetry at the population level might be a useful index of environmental stress in this seabird. The spectacular bilaterally expressed facial plumes displayed by Whiskered Auklets provide an interesting test case for questions about asymmetry in sexually and naturally selected traits.

  PublisherDOI

• Whiskered Auklet Asymmetries

  Figshare · 2023-01-01 · 1 citations

  datasetOpen access

  Data and R code for a manuscript on the symmetry of ornmental plumes in the Whiskered Auklet (<em>Aethia pygmaea</em>). In this species males and females display on their faces four elaborate feather ornaments that serve both courtship and mechanosensory functions: three bilateral pairs of white facial plume tracts (superorbital, suborbital, and auricular) and a slender black forehead crest, each comprised of several filoplumes. We studied left-right symmetry in the three antenna-like bilateral white head plumes of 721 wild-caught marked individuals (162 of known sex, 94 of known age that were 1-16 years old) during 1992-2009. We looked for effects of age, sex, body size and condition on ornament asymmetries. We also looked for correlations between population average asymmetries (fluctuating asymmetry) and both ocean climate and measures of survival and productivity in the preceding 2-3 yeasrs.

  PublisherDOI

• Extensive variation in feather ornaments of Whiskered Auklets in the Aleutian Islands reflects age, sex, condition, and geography

  The Auk · 2022-01-04 · 2 citations

  article

  Abstract Both sexes of Whiskered Auklets (Aethia pygmaea) display the most elaborate feather ornaments of any seabird: a slender black forehead crest, and 3 bilaterally symmetrical pairs of white facial plumes (superorbital, suborbital, and auricular). We studied patterns of ornament variation in 796 banded individuals (147 of known sex, 254 of known age from 1 to 16 years) during 1992–2009 at Buldir Island (principally), and 3 other Aleutian Islands (Davidof, Ulak, and Egg) in Alaska, USA. As expected for socially selected traits, ornaments were more variable across individuals than anatomical traits in size but with only slightly male-biased sexual dimorphism. Body condition index increased from age 1 to 3 years but changed little thereafter. Even within birds ≥4 years old, ornament size was positively related to body condition index. Subadults (one-year-olds) had smaller ornaments than adults (age 2–16 years) but there was no further change in ornament size as adults aged and no evidence of senescence even in the oldest birds (&amp;gt;8 years old). Nonetheless, overall ornament size varied from year-to-year at Buldir and was correlated with indices of both ocean climate and auklet productivity in the preceding 2–5 years. From Buldir to Egg Island (1,266 km), the size of both anatomical and ornamental traits increased by 5–15% except for bill depth, which was largest in birds from Buldir and Egg at opposite ends of the Aleutian breeding range. This study is one of few to examine patterns of ornament variation in a long-lived, socially monogamous bird, even though such patterns are crucial to understanding the relationship between sexual selection and life history.

  PublisherDOI

• Global Financial Stability Report, April 2021

  International Monetary Fund eBooks · 2021 · 2 citations

  • Business
  • Finance
  • Financial system

  The Global Financial Stability Report (GFSR) assesses key vulnerabilities the global financial system is exposed to. In normal times, the report seeks to play a role in preventing crises by highlighting policies that may mitigate systemic risks, thereby contributing to global financial stability and the sustained economic growth of the IMF's member countries.

  DOI

• Indirect effects of invasive rat removal result in recovery of island rocky intertidal community structure

  Scientific Reports · 2021 · 42 citations

  • Ecology
  • Biology

  Eleven years after invasive Norway rats (Rattus norvegicus) were eradicated from Hawadax Island, in the Aleutian Islands, Alaska, the predicted three-level trophic cascade in the rocky intertidal, with native shorebirds as the apex predator, returned, leading to a community resembling those on rat-free islands with significant decreases in invertebrate species abundances and increases in fleshy algal cover. Rats had indirectly structured the intertidal community via their role as the apex predator in a four-level trophic cascade. Our results are an excellent example of an achievable and relatively short-term community-level recovery following removal of invasive animals. These conservation successes are especially important for islands as their disproportionately high levels of native biodiversity are excessively threatened by invasive mammals.

  PublisherOA PDFDOI

• Who saves money buying electric vehicles? Heterogeneity in total cost of ownership

  Transportation Research Part D Transport and Environment · 2021 · 125 citations

  • Business
  • Agricultural economics
  • Environmental economics
  PublisherDOI

• The Making of Zero Curves

  SSRN Electronic Journal · 2021-01-01

  articleOpen accessSenior author
  PublisherDOI

• Whiskered Auklet (Aethia pygmaea)

  Birds of the World · 2020-03-04 · 2 citations

  reference-entrySenior author
  PublisherDOI

Frequent coauthors

• Brian D. Wright

  University of California, Berkeley

  39 shared

• Rachael E. Goodhue

  University of California, Davis

  19 shared

• G. Vernon Byrd

  Consumer VOICE

  15 shared

• Ian L. Jones

  15 shared

• Kristiana Hansen

  11 shared

• Richard E. Howitt

  10 shared

• Anne E. Peck

  New Mexico State University

  9 shared

• Aaron Smith

  8 shared

Education

• Ph.D.

  Yale University

  1980

• Other

  Yale University

  1977

• B.A.

  Williams College

  1975